Exemplary embodiments of the invention relate to a dual-clutch transmission.
German patent document DE 10 2007 049 257 A1 discloses a dual-clutch transmission having two input shafts provided for connection to a power shift clutch, having at least one countershaft that is offset in parallel to the input shafts, an output gearwheel designed as an idler gear and situated coaxially with respect to the countershaft, at least one gearwheel plane having an idler gear that is situated coaxially with respect to the countershaft, and a shifting unit having a first shift position in which the output gearwheel and the countershaft are connected to one another in a rotationally fixed manner.
Dual-clutch transmissions are likewise known from the publications DE 10 2009 018707 A1 and DE 10 2011 000152 A1, related to the same species, having two input shafts that are provided for connection to a power shift clutch, having at least one countershaft that is offset in parallel to the input shafts, an output gearwheel designed as an idler gear and situated coaxially with respect to the countershaft, at least one gearwheel plane having an idler gear that is situated coaxially with respect to the countershaft, and a shifting unit having a first shift position in which the output gearwheel and the countershaft are connected to one another in a rotationally fixed manner. These dual-clutch transmissions also have at least one additional gearwheel plane (Z4a, Z5a; Z4b, Z5b), which in at least one forward gear (V1a, V1a′, V1b, V1b′) and/or at least one reverse gear (R1a, R1a′; R1b, R1b′) is provided together with the first gearwheel plane (Z1a; Z1b) for transmitting a force flow and/or power flow.
Exemplary embodiments of the present invention are directed to a dual-clutch transmission having two input shafts provided for connection to a power shift clutch, having at least one countershaft that is offset in parallel to the input shafts, an output gearwheel designed as an idler gear and situated coaxially with respect to the countershaft, at least one gearwheel plane having an idler gear that is situated coaxially with respect to the countershaft, and a shifting unit having a first shift position in which the output gearwheel and the countershaft are connected to one another in a rotationally fixed manner.
The shifting unit has a second shift position in which the idler gear and the output gearwheel are directly connected to one another in a rotationally fixed manner. A simple and compact dual-clutch transmission having a large number of forward gears and a small number of shifting units may be implemented in this way. An “idler gear” should be understood to mean a gearwheel that is situated so as to be rotatable with respect to a shaft, and which is provided for being connected to the shaft in a rotationally fixed manner. This is understood in particular to mean a gearwheel that is permanently connected in a rotationally fixed manner solely via one coupling element of a shifting unit. Furthermore, an “output gearwheel” should be understood to mean a gearwheel that meshes with a gearwheel of an axle drive. In addition, a “shifting unit” should be understood to mean a unit that is provided for connecting at least one idler gear and one shaft and/or two idler gears to one another in a rotationally fixed manner. The term “directly connected in a rotationally fixed manner” should be understood to mean that the idler gear and the output gearwheel are not connected to one another by means of the countershaft, but, rather, are rotatable with respect to the countershaft in the second shift position. The term “provided” should be understood to mean specially designed and/or equipped.
In addition, the dual-clutch transmission includes at least one additional gearwheel plane, which in at least one forward gear and/or at least one reverse gear is provided together with the first gearwheel plane for transmitting a force flow and/or power flow. The appropriate forward gear and/or the appropriate reverse gear may thus be shifted as a so-called winding gear, as the result of which a large number of gears may be achieved with a small number of gearwheel planes.
According to the invention, the dual-clutch transmission has a total of five gearwheel planes maximum and a total of five shifting units maximum, which are provided overall for shifting at least eight forward gears and at least one reverse gear. The dual-clutch transmission may thus have a particularly compact design, and at the same time may have an advantageous shifting logic system.
Furthermore, in accordance with an exemplary embodiment the shifting unit can have a synchronizing element that is permanently connected to the output gearwheel in a rotationally fixed manner. An advantageous shifting logic system may be implemented in this way. A “synchronizing element” should be understood to mean an element of the shifting unit that is provided to accommodate a sliding sleeve of the shifting unit in a rotationally fixed manner in a neutral position, the sliding sleeve being axially displaceable with respect to the synchronizing element. The term “permanently connected in a rotationally fixed manner” should be understood to mean a nonshiftable, rigid connection by means of which the synchronizing element and the output gearwheel always have the same rotational speed.
The idler gear is preferably situated in the axial direction between the synchronizing element and the output gearwheel. The shifting unit may thus be situated in a particularly advantageous manner. The term “in the axial direction between” should be understood to mean that the idler gear is situated between the synchronizing element of the shifting unit and the output gearwheel, along an axis of rotation of the countershaft.
Additionally, in accordance with an exemplary embodiment the idler gear is rotatably mounted on the output gearwheel and/or the synchronizing element. Advantageous mounting of the output gearwheel, and at the same time an advantageous arrangement thereof, may thus be achieved for the idler gear. A connection between the output gearwheel and the synchronizing element preferably passes through the idler gear.
In one advantageous embodiment the shifting unit has a coupling element that is permanently connected to the countershaft in a rotationally fixed manner, and a coupling element that is permanently connected to the idler gear in a rotationally fixed manner. In one particularly advantageous refinement, the shifting unit has three shift positions and one neutral position. The number of shifting units may be further reduced in this way.
One of the additional gearwheel planes particularly preferably has an idler gear that is situated coaxially with respect to the countershaft, and the shifting unit has an additional coupling element that is permanently connected to the additional idler gear in a rotationally fixed manner. The three shift positions may thus be shifted by means of the one shifting unit, as the result of which a large number of gears, and at the same time a small number of shifting units, may be achieved in a particularly simple manner.
Furthermore, in accordance with exemplary embodiments all gearwheel planes have a fixed gear that is permanently connected to one of the input shafts in a rotationally fixed manner. In particular, it is advantageous for the dual-clutch transmission to have an additional countershaft which is offset in parallel to the one countershaft and the input shafts, and an output gearwheel which is permanently connected to the additional countershaft in a rotationally fixed manner.